Exercise is important to the long term control of obesity in children. In previous research we have demonstrated that a lifestyle exercise program is associated with superior long term weight control compared to an isolcaloric structured aerobic exercise program. However, even in the lifestyle exercise program children do not adhere to exercise throughout treatment. One of the major reasons for the difficulty in maintaining increased exercise may be the failure to consider that obese children often prefer sedentary activities such as television watching to more vigorous exercise, and in most situations would choose to be sedentary rather than active. The present study is designed to assess the effects of a comprehensive exercise program that includes both increasing lifestyle exercise as well as decreasing sedentary activity on long term weight control Children will be randomly assigned to one of four groups that vary according to whether they are provided a lifestyle exercise program and/or a program designed to reduce sedentary activity. Children will be followed over a three year period, to provide data on differences in both the short term and long term differences between the groups. In addition, measures of exercise adherence, exercise preference, and laboratory assessment of the relative reinforcing value of vigorous or sedentary activity will be used to understand how these variable influence weight change.